1. Field of the Invention
This invention relates to boat hulls, and more particularly, to mono-hull, channel bottom boats having curved sides and finely, contoured channels extending along both sides of the keel. The channels have a venturi structure defined continually along their length. The fore sections have roll-under planes that deflect water flow, completely under the channels and into the venturi structure, during passage, thereby introducing extended laminar flow and a Controlled Flow Feature. The bow sections have finer entry angles which substantially reduce "wave-making" boat hull resistance.
The boat hull design also introduces a pair of deeply rockered, or deeply descending chines, extending laterally and aftwardly from the upper part of the bow which may descend downward below the bottom of the keel. The deepness of the chines harbor a large volume of relative still water, (in respect to lateral movement) trapped within the channels, which the boat cannot climb over, and which accomplish pronounced lateral resistance, by having inherent static inertia compounded by venturi flow aftward to the direction of forward movement.
The rolling-under by the bow and chine planes absorb much of the shock of the head waves rendering it possible to incorporate relative flat buttock lines along the length of the channels, which have low resistance to forward movement.
A Controlled Flow Principle is hereby introduced to boat hull design.
This invention applies to all marine designs, from surf boards to deep-displacement merchant boats, or whatever, all having a reduction in resistance per displacement and improved sea going qualities.
2. Related Art
The total resistance of a boat can be placed into two parts; "Skin friction" resistance S/F (viscosity drag), and Form Resistance; sometimes called "wave-making" resistance W/M. "Skin friction" and "wave making" resistance we see as wake and it represents the water dragged along by the boat hull.
"Skin friction" S/F accounts for the greater part of resistance at slow, below planing speeds whereas "wave-making" W/M resistance accounts for the greater part of resistance at faster, above planing speeds; in all conventional boats.
Resistance of a boat hull may be either laminar flow in character, resulting from finely contoured or concave flow lines; or turbulent flow in character caused by convex flow lines.
Concave lines tend to "hug" the water because the following impetus to water is always greater than the inertia flow-out caused by the preceding impetus. Laminar flow prevails.
Convex lines force water flow away from the hull because the following impetus is always less then the inertia flow-out caused by the preceding impetus. Separation of flow is inevitable, with eventual cavitation of flow especially in the bow sections which will rewult in "sailing under".
Turbulent flow, for the most part, always prevails with all contemporary boat designs.
Additionally, we have two types of boat hull designs; deep displacement boats which are unable to surmount their head waves but "dig a hole in the water and sail under" when they are driven by wind or power beyond the limitation imposed by their water-line-limit, during passage; and surface planing boats which are able to climb up on their head waves and plane.
The deep displacement boats are limited in speed by roughly 1.5 times the square root of their water-line-length as stated in knots per hour, but are able to carry much more cargo and are more sea-worthy. The planing boats go much faster but, cannot carry as much weight and are subject to hammering and pounding during rough weather.
The Deep Chine inventive hull has flat buttock curves that do not rise up to the deck level; they merely end at the prow and may be held flat. Smooth laminar flow is maintained along the finely contoured bottom channels, buttock curves and converging waterlines. It can be claimed that substantially NO "white water" appears between the chines, during passage.
Contemporary boat designs, on the other hand, seem to rest in the de-controlled flow principle, with convex lines being predominant throughout the hull lines that produce turbulent flow, for the most part, even, with tri-bottom run-a-bouts. Modern boat designs have greater power per displacement but not less resistance per displacement.
Preoccupation with power accommodation seems to be the primary concern with contemporary boat designers, but design for less resistance, let alone extended laminar flow, has eluded boat designers until the appearance of the Deep Chine design.
It is therefore the chief object of this invention to provide an improved boat hull design that will substantially reduce overall water resistance per displacement during all speeds of passage and sailing conditions by introducing the Controlled Flow Principle. (CFP)
A major object is to establish and extend laminar flow along the entire length of the hull bottom and sides by a combination of specially contoured lines which maintain consistent hull pressure against the water passage, thereby ihibiting separation and the formation of turbulent flow.
A necessary objective is the formation of inverted channels having cross sections being either concave or flat, along the longitudinal length of the boat hull on both sides of the keel.
An indispensable further object is to provide a venturi flow effect with converging waterlines defining a venturi structure having a venturi mouth, a venturi throat and a exit area defined along the channels.
A further object is to roll, or deflect the bow and chine headwaves down and completely under the bi-lateral deeply inverted bottom channels creating generally level dual "WATER RAILS" out of the surface of the sea, for the boat to ride on.
An additional object is to position the boat hull on it's "WATER RAILS" where it can ride upon its quarter buttock and not on top of the bow waves during passage.
Another object is to apply the CFP to mono-hull boats having widely spaced chines thereby encompassing most of the water flow into the inverted channels.
Another object is to provide a venturi flow along the sides of the boat hull thereby limiting flow-out and establishing smoother flow along the length of the boat.
Yet another object is to entrap a large volume of relative still, or slow moving water inside the deep bottom channels such that the water cannot be easily accelerated laterally by virtue of the volume of water having inherent inertia, compounded by aftward movement, thereby accomplishing pronounced lateral resistance without the need for high-drag, underwater structures.
In keeping with the same object is to force head-wave water from both bow and chines to converge and overlap upon each other thereby cushioning the impact with head seas as well as augmenting laminar flow.
A further object is to prevent cavitation by the incorporation of sharper waterlines having minimal convexity thereby reducing the rate of acceleration of head waves away from the fore section hull planes.
A further objective is to minimize fore pressure and aft suction components of resistance by the incorporation of flat buttock lines having little longitudinal rocker along the hull length.
Another object is to provide fore sections having vertical shapes becoming lateral thereby providing shapes that deflect bow and chine water flow against each other thereby inhibiting outward flow.
Yet another object is to reduce the tendency of the boat to yaw, roll, bounce or pitch pole by keeping the centers of buoyancy and lateral resistance close together.
An additional object is to provide a boat hull design that will not "sail under" at any speed above it's water-line-limit.
Another object is to apply the CFP to different boat hull types including surf boards, surf board sailors, poly-hull boats such as catamarans and tri-marans.
Another object is to apply the CFP to deep-displacement marine structures such as merchant ships, tuna boats, tankers, military craft and specially designed boats that scoop up oil and debris.